Low-frequency Plasma-enhanced Chemical Vapor Research Articles

Effects of growth temperature on titanium carbide (TiC) film formation using low-frequency (60 Hz) plasma-enhanced chemical vapor deposition

TiC films were formed by low-frequency (60 Hz) plasma-enhanced chemical vapor deposition (LFPECVD) using TiCl4, CH4, and H2 gas mixtures. The effects of the growth temperature and feasibility for the on-glass deposition of TiC films were investigated. The growth kinematics of TiC films was controlled mainly by surface-reactions below 450 oC, and dominated by a mass-transfer process above 450 oC. The films exhibited a face-centered cubic structure, and the preferred orientation of film growth was mainly the (200) plane. The [C]/[Ti] ratio was over-stoichiometric below 400 oC, and became almost stoichiometric above 450 oC. The optical properties of the films were characterized by high reflectance in near infrared (NIR) region and a steep edge in the visible region, and the reflectance in the NIR region increased gradually with increasing temperature. As a result, LF-PECVD is a useful technique to acquire Cl-free TiC films at relatively low temperatures.

Effects of germane flow rate in electrical properties of a-SiGe:H films for ambipolar thin-film transistors

In this work, the study of germane flow rate in electrical properties of a-SiGe:H films is presented. The a-SiGe:H films deposited by low frequency plasma-enhanced chemical vapor deposition at 300°C were characterized by Fourier transform infrared spectroscopy, measurements of temperature dependence of conductivity and UV–visible spectroscopic ellipsometry. After finding the optimum germane flow rate conditions, a-SiGe:H films were deposited at 200°C and analyzed. The use of a-SiGe:H films at 200°C as active layer of low-temperature ambipolar thin-film transistors (TFTs) was demonstrated. The inverted staggered a-SiGe:H TFTs with Spin-On Glass as gate insulator were fabricated. These results suggest that there is an optimal Ge content in the a-SiGe:H films that improves its electrical properties.

Passivation of air-exposed AlGaAs using low frequency plasma-enhanced chemical vapor deposition of silicon nitride

The authors report on the development of a simple passivation technique of air-exposed AlxGa1−xAs using (NH4)2S treatment and low frequency plasma-enhanced chemical vapor deposition of silicon nitride. Metal-insulator-semiconductor capacitors were fabricated on p-AlxGa1−xAs substrates and characterized using capacitance-voltage and conductance-frequency measurements. Modulation of the surface potential is observed and unpinning of Fermi level is demonstrated. The minimum interface state density as estimated using conductance method is in the order of (2–3)×1012cm−2eV−1. The passivation potential of the low frequency plasma may be explained by the high level of hydrogen bombardment of the substrate.

Uncooled micro-bolometer based on amorphous germanium film

The fabrication and characterization of an uncooled micro-bolometer, in which the sensing material is amorphous germanium (a-Ge:F) is presented. In order to obtain thermal isolation, the micro-bolometer was fabricated on a silicon dioxide membrane, which was made on a silicon wafer by micro-machining techniques. The sensing layer was deposited from GeF 4 + H 2 mixture by low frequency plasma-enhanced chemical vapor deposition. The a-Ge:F film had high thermal coefficient of resistance at room temperature α=0.04 and moderate conductivity σ RT=2.5×10 −3 Ω −1 cm −1. The micro-bolometer was characterized by the measurements of current–voltage characteristics in dark and under infrared illumination with a black body at temperature T bb=1123 K. Thermal and noise characteristics were also measured. The micro-bolometer having the pixel area A d=60×60 μm 2 demonstrated thermal resistance R th=5×10 6 K W −1, current responsivity R I =6.2 mA W −1, voltage responsivity R V =4.2×10 6 V W −1 and detectivity D ∗=8×10 6 cm W Hz 1/2.